This invention relates to audio high fidelity cable wherein the wavelength of signals carried on the cable is generally longer than the length of the cable (i.e., a short-wire cable), such as in audio signal and high fidelity sound reproduction applications. The invention has particular application where the range of frequencies is greater than several octaves and therefore broadband random noise can have potentially significant impact on the fidelity of a complex signal carried by the cable.
It is common practice in audio frequency circuitry to provide a shielding sheath surrounding signal-carrying conductors between subsystems and within components of an audio system. It is conventional in shielded audio cables to provide a direct connection from a local ground to the shielding sheath of the cable in an attempt to terminate spurious signals to ground.
Conventional shielding provides protection against external noise sources by terminating the external signals that are coupled into the shield to prevent them from being inductively coupled from the shield into the signal-carrying conductors.
It is generally thought that if the shield is not grounded from direct current (d.c.) through radio frequency (r.f.), the efficiency of the shield will be reduced, and the r.f. noise induced from the shield into the cable will be increased. These are both undesirable effects. Therefore, the conventional solution in audio cable applications is to connect the shield directly to the signal ground or to the chassis ground.
However, there are evidently other sources of signal distortion in audio applications that are not completely understood and that conventional grounding does not address. What is desired is a technique for improving the perception of sound quality.
A search by the applicant for patents in the fields related to shielding techniques failed to uncover any patents which suggested the use of isolation techniques for shielding. To this end, a search was conducted among the U.S. Patent Office records relating to noise suppression and wiring, transmission lines and cables, including Class 174, Subclasses 32-36; Classes 307, Subclasses 89 and 91; and Class 333, Subclasses 4 and 6, for records as of summer 1994, and no relevant patents were uncovered.